How to Validate License Keys Offline in JavaScript
License key validation is essential for protecting software and ensuring only authorized users can access premium features. While server-side validation is common, there are scenarios where offline validation is necessary or preferred. In this guide, we’ll explore how to implement offline license key validation in JavaScript using the JavaScript License Key Validator library.
Why Offline License Key Validation?
Offline validation offers several advantages:
- Privacy: No data leaves the user’s device
- Performance: Instant validation without network requests
- Reliability: Works even without internet connection
- Simplicity: No server infrastructure required
Understanding License Key Structure
A well-designed license key typically includes:
- Product Identifier: Identifies which product the key is for
- Metadata: Embedded information (edition, expiry, activations)
- Checksum: Validates key integrity
- Format: Human-readable structure (e.g., XXXX-XXXX-XXXX-XXXX)
Implementation with JavaScript License Key Validator
The JavaScript License Key Validator library provides a complete solution for offline validation. Here’s how to use it:
Step 1: Include the Library
<script src="license-validator.min.js"></script>Step 2: Configure the Validator
const validator = LicenseValidator.create({
format: {
parts: 4,
partLength: 4,
separator: '-',
charset: 'ABCDEFGHJKLMNPQRSTUVWXYZ23456789'
},
checksum: {
algorithm: 'CRC32'
},
expiration: {
enabled: true,
gracePeriodDays: 7
}
});Step 3: Validate License Keys
const result = validator.validate('XXXX-XXXX-XXXX-XXXX');
if (result.valid) {
console.log('License is valid!');
console.log('Metadata:', result.details.metadata);
} else {
console.log('Invalid license:', result.error);
}Key Features
Format Validation
The library validates license key format against configured rules:
- Number of parts
- Length of each part
- Character set restrictions
- Separator format
Checksum Verification
CRC32 or custom checksum algorithms ensure key integrity and prevent tampering.
Metadata Extraction
Extract embedded information from license keys:
- Product ID
- Edition (standard, pro, enterprise)
- Expiration date
- Maximum activations
Expiration Checking
Validate expiration dates with configurable grace periods for offline scenarios.
Advanced Features
Blacklist and Allowlist
Maintain lists of revoked or allowed license keys:
validator.setBlacklist(['XXXX-XXXX-XXXX-XXXX']);
validator.setAllowlist(['YYYY-YYYY-YYYY-YYYY']);Custom Validation Rules
Implement custom validation logic:
const result = validator.validate(key, {
checkExpiration: true,
checkBlacklist: true,
customValidator: function(key, metadata) {
// Custom validation logic
return true;
}
});Best Practices
Security Considerations
- Never expose validation logic in client-side code (use obfuscation if needed)
- Implement additional server-side validation for critical applications
- Use strong checksum algorithms
- Regularly update blacklists
User Experience
- Provide clear error messages
- Show validation status in real-time
- Offer support for invalid keys
- Implement retry mechanisms
Use Cases
Offline license key validation is ideal for:
- Desktop applications with web interfaces
- Progressive Web Apps (PWAs)
- Offline-capable web applications
- Demo and trial software
- Client-side feature gating
Conclusion
Offline license key validation in JavaScript provides a privacy-friendly, performant solution for software protection. The JavaScript License Key Validator library makes implementation straightforward with comprehensive features and flexible configuration.
Ready to implement offline license validation? Get JavaScript License Key Validator and start protecting your software today.
